HD64F3437TF16 Datasheet, PDF (532/752 Pages) Hitachi Semiconductor – 12 V must not be applied to the S-mask model (single-power-supply specification), as this may permanently damage the device.

21.1.6 Mode Control Register (MDCR)
Register Configuration: The operating mode of the H8/3437SF is controlled by the mode pins
and the mode control register (MDCR). Table 21.4 shows the MDCR register configuration.
Table 21.4 Register Configuration
Name
Mode control register
Abbreviation R/W
MDCR
R/W
Initial Value
Undefined
(Depends on operating mode)
Address
H'FFC5
Mode Control Register (MDCR)
Bit
7
6
5
4
3
2
1
0
EXPE^*1
—
—
—
—
—
MDS1 MDS0
Initial value
—^{* 2}
1
1
0
0
1
—^{* 2}
—^{* 2}
Read/Write R/W^*2
—
—
—
—
—
R
R
Notes: *1 H8/3437SF (S-mask model, single-power-supply on-chip flash memory version) only.
Otherwise, this is a reserved bit that is always read as 1.
*2 Determined by the mode pins (MD₁ and MD₀).
MDCR is an 8-bit register used to set the operating mode of the H8/3437SF and to monitor the
current operating mode.
Bit 7—Expanded Mode Enable (EXPE): Sets expanded mode. In mode 1, this bit is fixed at 1
and cannot be modified. In modes 2 and 3, this bit has a fixed initial value of 0 and cannot be
modified.
This bit can be read and written only in boot mode.
Bit 7: EXPE
0
1
Description
Single-chip mode is selected
Expanded mode is selected (writable in boot mode only)
Bits 6 and 5—Reserved: These bits cannot be modified and are always read as 1.
Bits 4 and 3—Reserved: These bits cannot be modified and are always read as 0.
Bit 2—Reserved: This bit cannot be modified and is always read as 1.
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